What is the best way to determine whether or not a file is an image in PHP?

Question

I have a sever which people can upload files to. The problem is that some of the filenames are mangled (dont have any extension) and so I cannot immediately determine file type.

Answer 1

If you have the GD2 extension enabled, you could just use that to load the file as an image, then if it returns invalid you can catch the error and return FALSE, otherwise return TRUE.